Wafer-level optoelectronic probing technique on semiconductor devices and circuits have proved to be effective to extract the device/circuit parameters, such as response time, delay time, scattering parameters, etc. [M. Y. Frankel, S. Guta, J. A. Valdmanis, J. F. Whitaker, G. A. Mourou, IEEE Tran. on Microwave Theory & Tech., 39 (1991) 910.; S. L. Huang, C. H. Lee, H-L. A. Hung, IEEE Tran. on Microwave Theory & Tech., 43 (1995) 1281]. Among these techniques, the electro-optic (EO) probing is a very useful approach to measure the electric-field (E-field) in microwave circuits [K. W. Chang, W. V. Sorin, OSA Proc. On Ultrafast Electronics and Opto-electronics, 14 (1993) 220; M. G. Li, E. A. Chauchard, C. H. Lee, Picosecond Electronics and Optoelectronics, Spring-Verlag, (1986) 54]. For these measurements, only field strength is needed to obtain the required information. However, in some circumstance, such as the chamfered bending of a transmission line, patch array antenna, active region of devices, the field direction may also be important to be determined [T. Koryu Ishii, Microwave Engineering, 2nd ed., 1989]. Traditionally, antenna is used for the measurements of E-field, which essentially is far-field measurement, and will not satisfy the future needs of microwave circuit technology development. On the other hand, in most EO sampling techniques [M. Shinagawa, T. Nagatsuma, IEEE Tran. Instrum. Meas., 41 (1992) 375; H. Takahashi, S-I. Aoshima, Y. Tsuchiya, IEEE Tran. Instrum. Meas., 44 (1995) 956], only one laser beam is used to probe the E-field signal, that will make the sensitivity of the system be decreased due to the EO crystal is not in the direction of best interaction with E-field. In the worse case, take LiTaO.sub.3 crystal for example, if its c-axis is perpendicular to E-field direction and a probing beam propagates in y direction only (that is a common case if the crystal is y-cut and with a reflection coating on the bottom), it will not be able to sense any E-field signal. In this invention, a novel E-field direction measurement with high sensitivity is demonstrated. This technique can be also used to compensate the angle between the E-field and the best interacted direction of the EO crystal.